Most of these things are obvious - but I like checklists, so I put everything in.
Things for me
alarm clock
bandanna
camera
cap to go under helmet if it was really cold
chap stick
coffee cup
coffee pot
coffee
cooler
cups
face cloth
filter coffee maker
filters
flash light
fleece jacket
gloves
ground cloth
helmet
insulating pad to sleep on
jacket
jeans
kitchen stuff
lantern
long sleeved shirt
paper plates
paper towels
pillow
polypro shirt (for the ride - turned out to be the right thing)
pot holder
propane
riding boots
riding tights
shirts to change into
sleeping bag
stove
sun screen
t shirt
tea
tent
thermos
toilet paper
toiletries
towel
underwear
water resistant windbreaker - (2)
water, at least a 5 gallon container
wool socks
wool sweater - warm either wet or dry and packs up small
Things for the horse and trailer
alfalfa hay
baby food (to hide the electrolytes)
baby oil - applied along the girth area to prevent chafing
blanket, heavy
blanket, light
breast collar
broom
broom
buckets
Bute
carrots
crupper
electrolytes
Extra carabiners and ties
First aid kit
girth
grooming supplies
hackamore
heart rate monitor
hoof pick
hose
Ice boots
oat hay
paddock/corral/sky hook
rake
reins
rice bran
rope halter
rump blanket
saddle bag
saddle pad
saddle
splint boots
supplements
syringes
vaseline - to prevent "scratches"
water bottle and carrier
water buckets